The present invention relates generally to an electro-optical device for use in conjunction with obtaining a tan and, more particularly, to a programmable electro-optical device for monitoring time integrated exposure to optical radiation and indicating when preselected amounts of such exposure have been realized for the purpose of obtaining a desired tan in a controlled manner over a series of tanning sessions.
Factors which influence the tanning process have been the subject of intense investigation over the past several years due to the fact that excessive exposure to ultraviolet radiation, which is responsible for tanning, can be detrimental to the individual's health. It is now well established that certain regions of the ultraviolet spectrum are capable of inducing skin cancer (i.e. UV-B and UV-C). However, some exposure to solar radiation is beneficial not only psychologically, but also in the production of vitamin D through a photochemical reaction in the skin. Aside from these important medical considerations there are many painful and often embarrassing discomforts which are associated with uncontrolled or unmonitored exposure to solar or artificial radiation.
Obtaining a tan in an unprogramed or unmonitored way can result in erythema, or burning of the epidermal skin layer, giving rise to increased sensitivity and soreness of tender regions of the body such as earlobes, knees, joints, and in general any region of the body which is usually not exposed to solar radiation. The classical sunburn response or erythema begins immediately on exposure, and subsequently disappears. A delayed effect appears after a period of 2-4 hours later, reaching a peak in 14-20 hours subsequent to exposure, and may persist for 24-48 hours. Severe exposure can and indeed often results in desquamation, or peeling of the epidermis which results in a lighter skin pigmentation. Uneven exposure can result in uneven skin coloration. Current interest in "Tanning Salons" has resulted in the extensive use of special lamps which are used in suntan treatment and treatments of psoriasis and other skin disorders through phototherapy. The spectral output of these lamps contains strong emissions in the carcinogenic UV-B and UV-C radiation range. Thus it is extremely important to exercise proper caution when prolonged exposure to radiation for purposes of tanning is desired.
Since the tanning process comprises both an immediate and delayed tanning response, an individual is usually not aware of the delayed or cumulative effects of exposures. It is practically impossible for an individual to visually calibrate or even recognize quantitatively or qualitatively the radiation which is received during a tanning session. Moreover, it is apparent that the quantity of exposure cannot simply be related to the time of exposure, since the latter does not take into account that the intensity of solar radiation is directly affected by such factors as latitude or proximity to equator, altitude above sea level, earth-sun seasonal distance changes, weather conditions, time of day (e.g. UV-B transmission peaks between 10:00 A.M.-2:00 P.M., and is negligible before 8:00 A.M. and after 4:00 P.M.), etc.
Ideally, a knowledgeable sunbather should develop a tanning program or regimen which is based on his individual skin type, and which will include the detection and calibration of his exposure to radiation, ensuring that each tanning session does not exceed the maximum erythemal dose of radiation, which is the dose that his skin type can sustain without injury.
It would also be highly beneficial for the individual to divide his required tanning exposure into the total time available to him for tanning so as to ensure a uniform sequence of exposures over the total tanning period available. In addition, "Tanning Salons" could make use of such a device in order to properly calibrate tans and insure the safe exposure of individuals to the artificial radiation from sun lamps. Thus, it becomes apparent that the achievement of a uniform tan or skin pigmentation in a carefully programmed and calibrated procedure without the hazards of sun burn or other deleterious effects of radiation is a desirable goal.
A number of devices are known for monitoring (human) exposure to UV radiation; however these devices are only for the purpose of preventing excessive exposure or preventing sunburn and not for the purpose of enabling a person to achieve a desired tan in a controlled and programmed manner and based, at least in part, on information personal to the user.
In U.S. Pat. No. 3,710,115 there is disclosed a sunburn warning device comprising radiation detection means, integrator means, measurement means and indicating means to advise the user of the amount of radiation received related to the time of exposure.
In U.S. Pat. No. 3,917,948 there is disclosed a device for measuring the radiation dose of natural and artificial irradiation, in particular in the erythemal-effective range of UV-radiation. The device contains an opto-electronic detector, an analog-to-digital converter and a pulse counter. The device is designed such that different intensities are continuously integrated during a determined period and that the sum of the integrated intensities is evaluated. The device works on one hand as a measuring instrument and on the other hand as an indicator if a predetermined dose is reached, signalling optically or acoustically this event and or shutting off the radiator.
In U.S. Pat. No. 4,016,424 there is disclosed a system for detecting ultraviolet (UV) radiation and particularly adapted for the detection of fire. Electrical pulses are produced at a rate proportional to the intensity of UV energy received by a UV detector tube. An alarm and/or control function is actuated only when the tube pulse rate and pulse rate duration correspond to predetermined values. In addition, the alarm and/or control function is inhibited when the detector tube is exposed to non-fire created UV energy.
In U.S. Pat. No. 4,010,372 there is disclosed a device for measuring the ultraviolet radiation in the UV-A and/or UV-B range with detector means for said ranges, switching means for considering the skin sensitivity, electronic means for evaluating the signals derived from the detector, means for displaying the intensity and/or the dose of the radiation and second switching means for selecting one or different quartz lamps in said ranges. This device is in particular adapted for digitally measuring the dose of harmful erythem effective UV-B radiation or the dose of therapeutic healing UV-A radiation. This invention further relates to a method for producing an calibrating said device, in particular the shunts contained in said second switching means which enables to select different quartz lamps with different line intensities.
In U.S. Pat. No. 4,065,672 there is disclosed an ultraviolet sensing device coupled with suitable electronics which is capable of mesuring the amount of exposure to ultraviolet light.
For purposes of tanning, it is important to realize that the pigmentation of human skin is the result of two factors, intrinsic skin color and inducible skin color. Although intrinsic skin color is genetically determined, induced or facultative skin color is the result of added melanin pigmentation due to solar or artificial exposure to radiation, and the latter's affect on the process of melanogenesis. Melanogenesis referes to the production of melanin by the melanocytes, or pigment producing cells that are found in the epidermis along with the keratinocytes or Malpighian cells which contain the melanosomes.
The term "suntan" refers to the skin color change induced by exposure to solar (or equivalent artificial) radiation. It is now known that UV-B (290-320 nm) is primarily responsible for most of the photobiological responses of the skin, while UV-A (320-400 nm) generally acts to enhance the injury as well as the carcinogenic potential of UV-B radiation. UV-C(200-280 nm), which is by far the most carcinogenic, is not present in the portion of the solar spectrum that reaches the earth due to the presence of ozone in the upper atmosphere which absorbs most of this radiation. Although UV-B is the most efficient radiation for tanning it has also been found to be carcinogenic and may be also highly effective in bringing about premature aging changes in human skin. Kaibey, et al., report that "Long-lasting, esthetically pleasing tans can be induced by irradiation with UV-A alone." Knowledge of the intensity of radiation and the integrated doses of UV-A, UV-B and UV-C is thus not only important for tanning purposes, but also for the prevention of skin cancer or other photobiologically induced skin disorders.
The tanning process may be divided into two distinct photobiological processes, immediate tanning and delayed tanning. Immediate tanning, also known as the Meirowsky phenomemon, involves the oxidation of melanin throughout the epidermis and usually occurs immediately upon exposure to radiation of 320-400 nm (UV-A) and to a lesser extent upon exposure to visible radiation 400-700 nm. Immediate tanning reaches a maximum within 1-2 hours subsequent to exposure and decreases from 3-24 hours thereafter. Immediate tanning basically involves the redistribution of existing melanosomes without production of new melanosomes.
Delayed tanning involves the production of new melanin and disintegration of melanosomes. The effective radiation for the delayed tanning occurs in the UV-B region (which is also responsible for sun burning) of the spectrum (290-320 nm). However it is possible to achieve new melanin formation through the application of larger doses of longer wavelength radiation as high as 700 nm. Pigmentation of the skin due to delayed tanning begins 48-72 hours after exposure to radiation, reaching a peak in 13-21 days, and gradually subsides over the next few months.
Since the structure of melanosomes is genetically determined, the genetic background of the individual determines the extent of melanin production subsequent to exposure to solar or artificial radiation. This genetic background can be divided into five categories.
1. Easy burn and no tan: Blue eyes, very fair skin, red hair, freckled skin.
2. Easy burn and slight tan: blue-green or hazel eyes, moderately fair skin, blond hair.
3. Burn and then tan (without generally burning on subsequent exposures): Brown eyes, brunette or olive skin, medium color skin.
4. No burn and good tan: dark eyes, dark hair (pigmented Caucasians and Orientals).
5. Never burn and markedly tan: markedly pigmented people (Blacks, Australian Aborigines).
The Minimal Erythema Dose (MED), is defined to be that dose of radiation which produces a minimally perceptible erythema or sun burn in an individual. The MED varies with wavelength of radiation. For UV-B radiation the MED for radiation of 290-300 nm is 20-30 mJ/cm.sup.2, while the UV-A radiation of 320-400 nm the MED is 20-30 J/cm.sup.2.
For the purposes of melanogenesis induction, or tanning, 50-100 mJ/cm.sup.2 of UV-B are necessary. Pathak et al., report that an exposure of from 2-5 MED at 297 nm in the UV-B region will produce a grade 2+ pink erythema and a moderate tan, (grade ++, medium brown tan), while an exposure of 10 MED at 297 nm can produce a grade +++, deep brown tan.
It is the general purpose of this invention to provide a device which is programmed to monitor a user's time integrated exposure to artificial or natural radiation and indicate the realization of different amounts of said exposure for the purpose of obtaining a tan in a safe and controlled manner. The device enables the user to follow a calibrated regimen which will result in obtaining a final skin pigmentation (tan) with or without use of filtering agents such as provided in suntanning lotions, or sunscreening devices. The individual initializes the device by entering personal information which will allow the program to classify the individual as to : (1) Individual skin type and sensitivity to radiation; (2) initial skin pigmentation; (3) Sun Protective Factor (SPF) of tanning lotion being used for that session; (4) total exposure time desired for session; (5) final skin pigmentation desired; (6) number of exposures over which desired tan is to be achieved, and any other pertinent factors which affect tanning and which may from time to time be updated in the program.
The device uses the information entered by the individual to determine the following quantities: (1) Total integrated exposure required by individual in order to obtain desired tan; (2) maximum exposure which is allowed for current tanning session (MED); (3) total time of exposure allowed under present conditions of source intensity and SPF lotion used; and (4) SPF factor of lotion that can be used by individual to allow exposure to be extended over desired length of session. The device also includes a "scan" feature which allows an individual to search, with the use of device, that location which will extend or decrease the session time to the desired value. Finally, the device includes an alarm for giving an appropriate warning when the preset dose for each session and the total dosage are achieved, and a preset "turnover" feature which can be used to divide the session into an equal number of intervals for the purposes of tanning the front of the body and the back of the body to the same extent.